The present invention relates to a method of controlling a hybrid electric automotive powertrain and in particular to a method of calibrating a clutch of the automotive powertrain.
A powertrain of an automotive vehicle may include a disconnect clutch between an internal combustion engine and other powertrain components. Typically, the clutch is pressure controlled. The clutch may be placed in a prestroked state. In the prestroked state, a stroke pressure places clutch plates close to contact without transmitting torque. When in the prestroked state, a small pressure increase from the stroke pressure will begin transmitting torque between the plates. By prestroking the clutch, the clutch may be more quickly placed in an engaged torque transmitting state.
The clutch may be calibrated to set the stroke pressure. If the stroke pressure is too high, the clutch will be overstroked. An overstroked clutch creates a drag force on the powertrain. The drag force reduces powertrain efficiency and increases wear on the clutch. When the clutch is overstroked, the clutch plates are brought too tightly together in the prestroked state and torque is transmitted prior to torque transmission being desired.
Some methods of calibrating the clutch use direct monitoring of the clutch, often via sensors that are otherwise not required. Other calibration methods commonly result in the clutch being overstroked, which may produce noise, vibration, and harshness that is objectionable to an occupant of the vehicle.